Effect of processing conditions on instrumental evaluation of nixtamal hardness of corn

Two varieties of corn (Blanco and Toluca) were cooked in water at boiling temperature (at a ratio of 1:3) for different cooking times (25 or 45 min) and concentrations of lime (0.0, 0.5 or 1.0%). The cooked corn was allowed to rest for 5 or 14 h, resulting in the nixtamal product. The nixtamal was tested for hardness utilizing the nixtamal puncture cell (NPC) connected to a texturometer. The parameters of hardness measured were the maximum force (MF) required to rupture the nixtamal and the modulus of elasticity (ME). It also were determined the moisture content of the nixtamal, pH of the nejayote and loss of solids into the nejayote. The concentration of lime, cooking time and corn variety had a highly significant effect (P < 0.01) on the MF and ME of the nixtamal. Both determinations correlated very significantly with the moisture content of the nixtamal (r = -0.94 and r = -0.96, respectively). The ME values correlated significantly (P < 0.05) with the loss of solids and pH of the nejayote (r = -0.881 and r = -0.858, respectively). The NPC was capable of detecting the difference in the hardness of nixtamal obtained under different conditions of the traditional nixtamalization process, where it could be a useful tool for further studies of this raw material in the production of corn tortillas. Nixtamal is the alkaline cooked corn in the process to make corn tortillas. Actually, nixtamal hardness evaluation is made subjectively by the operator of the process. Depending on the nixtamal texture are the masa and the tortilla texture. Therefore, with the nixtamal punch cell, nixtamal hardness can be measured instrumentally and a better control of the corn tortilla process could be carry out. In addition, with the nixtamal puncture cell it is possible to study any factor affecting the nixtamal hardness.